Anomalous helimagnetic domain shrinkage due to the weakening of Dzyaloshinskii-Moriya interaction in CrAs

TL;DR

This study reveals that in CrAs, weakening Dzyaloshinskii-Moriya interaction upon cooling causes unusual helimagnetic domain shrinkage, demonstrating a new way to control magnetic domain size via DMI tuning.

Contribution

It uncovers the role of DMI weakening in helimagnetic domain behavior and demonstrates domain size control through DMI manipulation in CrAs.

Findings

Helimagnetic domains shrink below 255 K, contrary to typical thermal effects.

Weakening DMI causes variation in helical wave vector and formation of domain boundaries.

Magnetic domain size can be tuned by adjusting DMI in helimagnets.

Abstract

CrAs is a well-known helimagnet with the double-helix structure originating from the competition between the Dzyaloshinskii-Moriya interaction (DMI) and antiferromagnetic exchange interaction $J$. By resonant soft X-ray scattering (RSXS), we observe the magnetic peak (0~0~$q_m$) that emerges at the helical transition with $T_S$ $\approx$ 267.5 K. Intriguingly, the helimagnetic domains significantly shrink on cooling below $\sim$255 K, opposite to the conventional thermal effect. The weakening of DMI on cooling is found to play a critical role here. It causes the helical wave vector to vary, ordered spins to rotate, and extra helimagnetic domain boundaries to form at local defects, thus leading to the anomalous shrinkage of helimagnetic domains. Our results indicate that the size of magnetic helical domains can be controlled by tuning DMI in certain helimagnets.